In many microwave and millimeter-wave (mm-wave) radio applications, high power broadband amplifier monolithic microwave integrated circuits (MMICs) are needed. To provide high power broadband amplifier MMICs, traveling wave amplifier (TWA) MMICs have been commonly used. To increase output power, two-stacked FET configurations have been widely used. Theoretically, the stacked FET configuration can be extended to configurations with three or more stacked FETs. However, when making configurations with more than two stacked FETs, amplifier stability seriously deteriorates at the highest operational frequency due to non-ideal common source grounding. Because of the instability issue, high power TWAs have been exclusively designed using the 2-stacked FET configuration. The 2-stacked FET configuration is only able to increase the operational drain voltage by a factor of two when compared with the conventional TWA.
It would be desirable to implement an N-stacked field effect transistor (FET) based traveling wave power amplifier for monolithic microwave integrated circuits.